1 ABSTRACT With the development of modern society and economics , environmental issues are coming to our attention more and more . Pollution caused by domestic wastewater is getting worse and well noticed .Sewage treatment is becoming very important and indispensable .This paper is focused on the process design in our country for domestic wastewater treatment , and select the best process scheme to make the treated water reach the quality that required . This design have adopted the OD process and the procedure is simple ,management is convenient ,do not need to add the first sinking pool , digestive system ,reducing building and operating expenses , realizing automation totally . At the same time , easy to manage ,making the water reach sewage discharge standard , accomplish the rational utilization of water resource. KEY WORDS : Grid Pumping House OD The Second Sinking Pool Nitrogen and phosphor removal 1 绪论1.1 课程设计题目城市污水处理工艺设计1.2 设计依据(1) 污水水量 (a) 拟建污水处理规模是平均流量为40000 m3/d ；(b) 城市污水主要包括居民生活污水和工业废水；(c) 城市混合污水变化系数：总变化系数 Kz=1.37 。(2) 进水水质BOD5=170mg/L；TN=35mg/L； TP=3.8mg/L；总碱度 =2000 mg/L。(3) 出水水质城市污水经处理后，就近排入厂区附近某河流。污水处理厂出水水质根据GB18918－2002《城镇污水处理厂污染物排放标准》的一级排放标准（B 标准），污水厂出水水质控制为：BOD5≦20mg/L； CODcr≦60mg/L； SS≦20mg/L；TN≦20mg/L； TP≦1.0mg/l 。1.3 处理程度2 污水处理程度是由对象和地区排放标准决定。1.3.1 进出水水质进出水水质见表 1。表 1 进出水水质BOD5(mg/L) TN(mg/L) TP(mg/L) 进水170 35 3.8 出水≦20 ≦20 ≦1.0 1.3.2 去除率设去除率为 E，则有E= ×100％式中：0C ——进水物质浓度；eC ——出水物质浓度。（1） BOD5去除率： E= ×100％=88.24％（2） TN 去除率 : E= ×100％=42.86％（3） TP 去除率： E= ×100％=60.53％...
